The use of lasers for endoscopic urologic surgery has been limited primarily to those lasers whose light can be transmitted through glass or quartz optical fibers. Lasers of this type include the synthetic noedymium-doped yttrium aluminum garnet laser crystal (Nd-YAG), argon ion, and argon pumped dye lasers. The pathologic conditions amenable to treatment by these conventional lasers include primary bladder cancer and urethral stricture disease. Obliteration of these lesions is accomplished through thermal coagulation by use of the (Nd-YAG) and argon ion lasers. Argon pumped dye lasers are capable of treating only bladder cancer by destroying cancer cells through cytotoxic photochemical reactions generated in the presence of a photosensitizer, such as hematoporphyrin derivative. The power output of the latter type of laser is insufficient to thermally destroy a lesion under treatment.
To Applicants' knowledge, none of the above types of endoscopic laser instruments and their associated methods of treatment were found to be any more effective than conventional modes of therapy. Currently, transurethral resection with electrocoagulation is the primary treatment for superficial bladder tumors. Approximately sixty percent of the tumors treated by this method alone will re-occur with such reoccurrence being more frequent for those tumors larger than a centimeter in diameter, those that are multifocal or those that have reoccurred previously.
External beam or intravesicle radiation therapy has proven ineffective for the treatment of superficial bladder cancer. Intravesicle chemotherapy, i.e., repeatedly instilling cytotoxic chemotherapeutic agents into a bladder, constitutes a second-line mode of therapy when transurethral resection fails to control recurrences. The latter form of therapy controls recurrences in approximately twenty-five to forty-five percent of the cases, but involves multiple bladder catherizations, extending over a period of up to two years, with weekly catherizations required during the first six weeks of therapy.
In the treatment of superficial urinary bladder cancer, recurrent modes of laser treatment by conventional techniques have proven ineffective for the elimination of recurrence of the disease after treatment as compared with other forms of conventional therapy of the type described above. The (Nd-YAG) laser is suitable for treating selected patients with superficially urinary bladder cancer as outpatients, but may not be cost effective primarily due to the high cost of the laser system required. Argon pumped dye lasers require the presence of a photosensitizer to generate a cytotoxic photochemical reaction in order to destroy cells. A potential advantage of this form of surgery is that the cancer cells or tissue will be destroyed selectively because of the preferential absorption and/or retention of the photosensitizer by the cancer cells or tissue.
To date, it appears that well differentiated superficial cancers, the most common kind, respond poorly to the latter form of therapy. Also, hematoporphyrin derivative, the most widely used photosensitizer, is retained by the skin for approximately two to four weeks to thus require a patient to avoid direct sunlight for at least a four week period of time. Retreatments, if frequent, become vexing to a patient.
The CO.sub.2 laser overcomes many of the shortcomings of the other types of above discussed lasers. For example, the CO.sub.2 laser is very efficient in terms of power generation, enables laser lesions to heal with a minimal amount of scar formation, does not require a photosensitizer to effect its cytodestructive effects, and is substantially less expensive than the (Nd-YAG) or argon ion laser systems of equivalent power output.
The recently developed irbium doped yttrium aluminum garnet laser (Er-YAG) has some of the advantages of the CO.sub.2 laser in that it produces a 2.96 micron wavelength light which is also strongly absorbed by water and thus will probably have the same effect on tissue as the CO.sub.2 laser. In addition, the shorter wavelength light can be transmitted through fluoride glass fibers. A disadvantage is limited power generation and the requirement that the laser be pulsed. These latter two disadvantages may be solved with further development.
Various endoscopic instruments have been proposed to take advantage of laser capabilities for the purpose of treating maladies of the type described above. For example, U.S. Pat. No. 4,583,526 discloses an endoscopic instrument that uses a CO.sub.2 laser and a bundle of relatively inflexible optic fibers (chalcogenide glass) for performing laser surgery. The instrument is not conducive for optically viewing and surgically treating all portions of the inner wall of a bladder, for example, and will tend to change the character and divergence of the laser beam when the fibers are necessarily bent to the small radii of curvature necessary to effect the surgical procedure.
Similar problems arise in respect to the endoscopic laser instrument disclosed in U.S. Pat. No. 4,313,431 wherein an optical fiber must be bent during use to limit its area of application and adversely change its character and divergence, i.e., change in "spot size" of the laser beam due to bending of the fiber. It should be noted in this respect that the polycrystalline fibers are more prone to deform and/or fracture when they are bent to small radii of curvature, in contrast to more flexible glass fibers used in other types of lasers.
U.S. Pat. No. 4,141,362 discloses an endoscopic laser instrument which attempts to avoid the optical fiber bending problem by positioning a pivotal mirror within the instrument to reflect laser light within the viewing field of the endoscope proper. However, the viewing field as well as the area on which the laser beam can be impinged upon is severely limited. Also, the laser beam apparently passes through an optical window at an oblique angle that changes the beam's character and intensity. In addition, the patent fails to disclose means for insuflating a viscus and evacuating smoke.